I swear by my Spyder, but have had cause to swear AT it recently.....they DO have reliability problems....If you look at some of the fansites eg :
http://www.ottersccustoms.com/trouble.html#burping
you'll see that it's freely admitted that the Spyder has reliability issues...I stripped, cleaned and fitted a new Turbulence bolt to my Xtra, and it has never recocked since.....a friend had a Sonix which had never recocked since he bought it, no matter WHAT he did to it...
I've now managed to cannibalise parts of both and now have a SoniXtra which performs like a dream!
Spyders are great starter markers, they look good, they feel good, if you get a good paint to barrel match they're accurate and they have a great rate of fire...but be ready for potential gremlins, especially if you try to mod them! However, Havoc Paintball seem to have a very reasonable servicing..erm...service.
I also own an automag, but having just bought it and had the walk-on rained off today
I can't comment on the performance!
Have fun finding the marker for you, and though I hate them, don't discount the Tippman 98, 1,000,000 lemmings can't be wrong