ICD:
pop pop pop pop chop chop chop pop pop chop pop chop chop chop
The maintainence on a Matrix really isn't that bad. It is like a five minute job to lube it, every few weeks, and if something goes wrong, you know what it is- an o-ring.
Now, the stock efficiency is appalling, the looks are goofy, and it is a bit heavy, but you can do a lot to improve efficiency, you come to love the ugly billboard look (it cleans up fast!), and you can always hit the gym.
Every gun has some serious drawbacks, and anyone who has no reservations about their marker is probably being a little dishonest with themselves. I have owned a lot of markers and never had one tht worked every time I picked it up without the occasional issue. My team used to shoot Angels, and they had problems just like anything else.
The key is finding a marker whose faults don't bother you (much). The proliferation of excellent competitive markers is such a wonderful thing- every marker gets so much better because of the competition between manufacturers.
Any of those John C listed I would play with and be content with. I wouldn't want to pay for all of them, but that's taste for you.