What I use my Traveller 5.0 for, and what I appreciate about Traveller 5.09...
First off - when I received my two copies of T5 (Hard cover) - I was prepared to run the game as its own system. I purchased several of the Imperial Starbust dice and was eagerly looking forward to a new era of Traveller.
Sadly, that never came to pass as both and my best friend agreed that T5 was not yet ready for prime time. That having been said, the use of T5 as a reference work was such that I was still glad I spent the money supporting the launch of T5. Getting T5.09 made it a little better, but still not something I'd try to referee or want to play in.
When T5 finally tackled the ticklish issue of Fiefs for the nobility of the Imperium, I thought "GREAT!" Now - I'm wishing that a little more forethought had gone into the stages of Traveller as an ongoing thing instead of a fly in amber kind of thing. For instance. If you have specific criteria for a Baron to be present on a world, that's fine. However, if you have a world with a Duke, and the world profile has to be of a given set before it has a Duke - what happens when the world is not yet in the sweet zone for having a duke? Does it have a Count instead? There is no progression from a world when it first starts out as a colony world, then phases into what amounts to be a home world, and then finally, what it is like in the year 1105. This however, is a minor blemish in my eyes.
When I went searching for how T5 handles accuracy in jump, I looked at it in horror. Anything in which the distances exceed 1 week's travel in normal space is going to likely require the use of a jump drive to traverse in a star system. If you aim for a world that is in an orbit akin to Earth's orbit, but can end up being multiple weeks to months away due to the jump accuracy value - seems more than a wee bit off to my way of thinking.
Ultimately? I expected to be able to describe the CT universe using the T5 rules - something that unfortunately, is not 100% true. In the CT universe, a ship needed only to worry about whether it was within 10 diameters, 100 diameters or greater than 100 diameters of the nearest object. If outside of 100 diameters, it could enter jump space safely. No "If there is an object large enough to precipitate you out of Jump space between here and there - your Jump is cut short". The only time having a body within 100 diameters of your ship is when you attempted to exit jump space and enter normal space. That's it. CT's universe was a little less complicated.
If the intent for Jump Shadows and such were intended to force ships to spend more time in normal space - there were other ways that this could have been achieved without changing the mechanics of a Jump Space into a Hyper Space like feel. <shrug>
The skill system, even if it were "skill bloat" as compared against previous skill systems in any of the prior Traveller systems - was something I could easily accept. I've been a GURPS player for a fairly long time (over 30 years now) and that doesn't faze me. But any combat system has to be something that is intuitive for the players gathered at the table, or it is going to be a real pain teaching it and maintaining it. That is largely why we, as gamers, eschewed the use of T5.0, as well as T5.09. Hopefully, T5.10 will smooth the rough edges out.
In the end? T5 has a fairly large swath of ideas that can add to any Traveller Campaign regardless of the game system you use for your campaigns. I constantly raid other game systems for use with my current GURPS TRAVELLER campaign, and T5 in my eyes, was worth picking up for that reason alone. If/when T5 (what ever version it takes/requires) can handle the "conflict resolution" details with ease, is likely when I'll give it a spin. I'd like to see how well the ship design system works not just to describe a ship per se, but to handle the ship to ship combat. Until then - T5.XX will have to wait.
Will I buy a T5.10 book? Until I get a job, no. Even then, Martin's work has a higher draw on my discretionary funds than T5.10. Once I get a copy of the PDF - and can take it for a test drive, I likely will not purchase a copy of the book. If on the other hand, T5.10 does what I hope it does, then I will have to switch over from GURPS just to see how it does.
Having gone through heart procedures myself, I can only empathize with Marc for the time he had to recover from the procedure. That he's still plugging away on his product and trying to make good some of its shortcomings - all without making the prior backers pay for the updates, makes him a good man in my eyes. Granted, he has always been a decent human being from all of my past dealings with him. For that reason alone, I regret that I'm not in a position to support his next kickstart.