Spyder Electra and a few Autocockers (only tested). I prefer the Ion to all of these.
Smart Parts Ion with Halo B Rip Drive Loader and Freak Jr. System (comming soon)
Tippmann 98 Custom with Qloader System and J+J 16" Ceramic Barrel
Upgraded Feed Neck, Halo B w/ Rip Drive or Empire Reloader B (both are plenty fast and seem identical to me, just a matter of eye vs. sound activation). I also recommend the Blackheart board if you do some serious tourament play (only a 3 BPS upgrade but tourney features are nice.)
Reliability, Speed, Consistency, Upgradability, Playability, and Cost
Problems with Standard Feed Neck (very Minor)
Background: I have had a 98 Custom for three years, always preferring woodball over speedball, modding my gun for use as a sniper front/middle man, using stealth and accuracy to get over the slow ROF of the Tippmann. I would play speedball as well, but my woodball gun couldn't keep up. After days of research, I decided on the Ion.
The Gun: I went to the proshop and bought the stock Ion for $290, along with a cheap 47/3000 tank for $80, and a Halo B with Rip Drive for $125 (also excellent BTW). I convinced the guy behind the counter to gas my tank for free and took it all home. When I opened up the box, I turned down the output pressure (just to be safe), screwed on the barrel, and gassed it up. The gun instantly cocked and became ready. It was easy to turn on and even easier to deactivate the eye (same button does it all) and I dry fired the gun on semi. It was very quiet and very fast. The tank did make it back heavy, so I would recommend a drop forward or remote line. I then took off the trigger guard and tried to switch it to ramping to test it out. I click it onto ramping easily, but couldn't figure out how to save settings. Just pull the trigger. Any changes are saved and you can now fire the gun. The gun responds beautifully on ramping mode. Even without trigger adjustments the gun is a dream. I then adjusted my trigger to give it about a millimeter of pull. When walking, I do not notice the movement of the trigger at all. The only downside to the gun is the feed neck. The stock feed neck is so tight that the loader I got (Halo B) wouldn't even fit in. By removing the two larger O-rings inside the neck, the loader fits in fully, but still very, very snug. If you do this and are using a Halo B, it will never fall out, and is actually difficult to remove, making it safe for even the roughest play. I recommend buying the upgraded feed neck because it fixes the size issue and lowers your hopper to prevent hopper shots.
The Field: The next day, I took it to the local speedball field, using the POS white box paint offered at the pro shop for $35 bucks a case. The gun was amazing. The accuracy on the stock barrel is the best for a stock barrel I've ever seen, even with the sucky paint. With only a two foot spread down the length of the field, and under a foot spread across the field's width, a barrel upgrade can definitely wait if you're short on cash. The first game I played with it was two on three with me on the team of two. I left my partner behind at break and got two kills in fifteen seconds, one was using another Ion and the other using an E99. My partner got the third. Throughout the day I shot a little over a case of paint, never breaking once. This pumps out paint fast and is a sure way to prevent the other team from moving up while allowing you to do so yourself. Definitely bring pods! The only problem I had was shooting in my barrel condom due to either forgetting to turn off my gun or hitting the trigger accidentally (I have it really light). The regulator eventually breaks in and goes from ±6 fps ±2 fps at chrono. Great gun.
The Ion is one of the best guns I have ever used, and it's certainly the best deal. With the speed, reliability, and features of many $1000 guns, there's nothing to lose buy getting the Ion. I would never buy anything else.