A .40S&W is a great choice. It is much easier to find ammo for right now and cheaper too (local WallyWorld still has Blazer Brass 40 coming in every week for $11.47 for 50; no dice on 45ACP).
The S&W M&P is an obvious and excellent choice in a new gun, the 3rd Gen Smiths (full size 4006, 4046, or compact like the 4053, etc.) are superior pistols in every respect and easy to find cheap these days (bunch of 4046's locally for under $300 right now). Plus, unlike all the usual 1911 advice, you can just buy the gun and shoot it, you don't need all the aftermarket smithing, accessories, blah, blah, blah. That's what turned me off of the 1911 for so long until S&W came out with a decent target model you could just take out of the box and shoot.
I would also recommend the HK USP full size, but it's not cheap. I have both the compact and the full and prefer the full size for the range.
The only 40S&W I would not recommend is a Glock only because of the "issues" with them in 40, but many do seem to like them, but then again, I'm solidly in the hate 'em camp when it comes to that brand (yeah, they 'go bang every time...big whoop, so do 3rd Gen Smiths. They just don't go BOOM!).