Not a Bad Deal
The previous reviewer makes some very good points regarding the quality and versatility of an AT4040 paired with an SM57 (the latter of which you really should have if you've been recording anything. And even if you haven't, then an SM57 is an absolute must-have.)
There are a few microphones that match and/or exceed the quality of an AT4040 at a bit better price point—though this is admittedly purely a matter of opinion because any recording engineer knows that $$$ means zilch when it comes to getting the 'right' sound. It's about 'what sounds right for what you're doing,' not the moolah spent to buy it. Heck, Bono sang into an SM58 on U2's most recent album! Thom Yorke prefers an Electrovoice RE20 dynamic (broadcasting) mic. A far cry from an esoteric $8,000 vintage Neumann U87! So, go with your ear. Always.
I've played some live venues with these same pencil condensers offered by Samson, and I was pleasantly surprised by their sound. Particularly at this price point. And my personal preference for drum overheads when recording is Royer ribbons, Neumann U87s, and lately AKG 414s. So, I know what sounds good. I've used 'em all. Or at least the ones that matter. And the Samsons truly are a decent bang for the buck. I imagine they'd likely do an acoustic guitar justice when miked up as a stereo pair.
The Sennheiser e609 is a very popular microphone for use on electric guitar amps and toms. I've seen Mick Fleetwood use them on his toms and they sounded fantastic. This is a mic that could be thrown into the 'must have' category alongside the SM57 if one plans on miking guitar amps.
I've had a little experience with the AT2020 and it's a surprisingly solid and versatile large-diaphragm condenser that's usable for everything from tracking vocals to acoustic guitars, and can even even serve as a nice 'ambience room mic' for adding fullness to a drum kit or, well, really anything.
If you're truly new to microphones it's incredibly easy to get bogged down in the details. If possible, I recommend talking to people whose ear you can trust or, even better, audition the mikes yourself and see what you think. And remember, a great sounding preamp can make any mic sound richer and fuller. I've used some RODE valve microphones combined with my Avalon 737 and Trident channel strips while recording my $6,000 Taylor acoustic guitar, and it trumped a producer/friend's U87 with his esoteric pre.
Overall, if you're truly a beginner, this really is a great starting point. You can't go wrong here. If however you've already amassed even a few mikes, like say an SM57, and a decent large diaphragm condenser, then talking to a Sweetwater representative about how to best expand your mic collection further while saving the most money is my highest recommendation.