I've used the TH15As (they're rebadged Tapco Thumps) - they're decent, not as loud or quite as clear as the Mackies, but they're rugged, pretty lightweight, and sound perfectly fine for most smaller shows. I don't know if they have the same problem as the original SRM450s, which would occasionally overheat and cut-out when used as floor monitors due to poor ventilation. Never an issue on stands though, which is the only way I've used them. I'm considering getting some TH12As myself, as the smaller size and lighter weight appeals, although there's a lot of other good stuff on the market - I'm most seriously considering a DB Technologies rig at the moment.
I'm using TH12A's for my solo acoustic PA; they're super light and seem to have plenty of headroom and low end for my usual venues. The only thing I can compare them to are my previous 1st gen. JBL Eon 15's, and I think they sound better and seem to have more headroom. I only have to run the volumes at Unity, and get no noticeable hiss. I also have used them one at a time to amplify just my guitar, and the onboard EQ worked great.
Since I sold my old Ultimate TS80 stands with my JBL's, and the Thumps are so much lighter, I got the cheaper, lighter TS70 stands, and they're working great too. I love being able to carry the Mackie's comfortably up and down stairs at the same time- I really got sick of lugging the JBL's into the house at 4am.
We'll see about long-term reliability, but as I can get a new one for $250 if I have to, I'm not extremely worried about them. Very pleased so far.