OK, T-tail vs straight tail: The T is up out of the prop wash, and so what happens is that on takeoff there is a speed at which the elevator suddenly become more effective (and just the opposite on landing). This leads to overrotation at first. You can learn to deal with it, no prob. But some people don't like it. When landing, you can plop the nose hard, too. In addition, the T requires more runway.
Turbo: The turbo Lances have some cooling issues (no cowl flaps). There is a mod to put louvres in the cowl, and that helps some, but it's far from a panacea.
Speed mods: Lots of Lances have speed mods to one degree or another. The gear fairings, flap gap seals and hinge covers do help some in low-speed handling, and may give you a couple of knots. The wing tips look cool. The LoPresti cowl aids cooling and gives you a few knots. But none of these things will turn it into a sporty speedster.
Club seating vs straight: Your call. Club is popular, but when I bought my second one I specifically sought out straight seats. Lots of people don't like riding backwards. The rear facing seats sit very straight up and don't recline, and in this airframe there's not enough footroom for two pairs of feet facing each other. Club is great if you're flying 3 or 4, not so great if you're flying 5 or more. (There is a 7th seat option for forward facing seating.)
Mechanical: Not much that's unusual. You might want to check the overhaul/replacement date of the hydraulic gear powerpack, as that's a costly part. Also check the integrity of the doors, particularly the fit of the top of the aft door. Lots of pax slam it with the latch extended, bending the bejesus out of everything. You can bend it back, but that doesn't make it good as new.
Make sure your checkout includes a flight at max gross. The airplane flies very differently loaded than it does with just two aboard and no bags -- ie a training configuration. It'll skate around a lot at rotation speed and really wallows on initial climb. Yes, you can takeoff at max gross on a 95 degree day, but you'll need runway and steely nerves.
What else?