I also was a classic BT player, and I prefer A2089 because it is more than just fighting anime-style mecha.
Basically, as we are all aware and try not to admit to ourselves, BT was fun for it's simplicity. No worries about radar lock. All missles are fire and forget. No real countermeasures. Sure there were cool ideas and neat toys for blasting your enemies, but that's about all it was.
A2089 is giant robot combat grown up. It's not as simple as BT, but it's got way more depth. Electronic warfare. Power availability determines what you can do each round, not a nebulous "heat" score. Countermeasures and smart armor. More realistic ranges. And to top it off it's an RPG to, not just a giant robot battle system.
Regarding the book itself, te artwork is average, except for the meks which are fantastic. some minor errors in the text, but easily worked around. All in all I highly recommend it if you want something with more depth of play than BT.