I picked up a pair of these [I always buy in pairs for stereo work] at my local store's annual clearance sale last week, and I've used them a few times now on various projects. I'll be comparing it directly to the Shure SM57 and Beta 57 so unless you have experience with those this won't help you... alsoyour opinion may vary.
First things first - this mic is light compared to the 57. It is metal, I assume aluminum except for the part that is attaching the grilles to the body, that part is plastic. Both grilles are metal. It feels fragile but I bet it could take a beating. Not as bad as a 57 because over 3/4 of this thing is the mesh grille. The mic clip is SUPER TIGHT. Which is no problem for me but some people might have a hard time getting it in or out. A standard vocal/instrument mic clip is too big for it.
I read online in various places how this mic is unbalanced. I read the schematic and it sure looks balanced to me.
Now onto the sound: This mic is rounder in the bottom end and smoother on the top than a 57. Is that good? Yes! Is it better? Totally subjective. If you find your sound a little shrill through a 57 then give it a try. If you record a bunch and are looking for a quality inexpensive addition to your mic locker, try it.
I found the extra roundness was a welcome addition for clean guitar, I actually prefered it over a 57. When I did some heavy palm muting in drop-d the roundness of the bottom end was a little bigger sounding than the 57 but not as tight - however the level stayed much closer to the un-muted parts, whereas the 57 jumped up in volume substantially. Another noticeable feature of the e609 when compared to the SM57 is the noise. A 57 has more "bite" to it, and I think that presence boost is one reason that the 57 picks up a lot of amp hiss. The e609 however is really quiet. It has plenty of top end but just doesn't seem to get a lot of amp hiss. As a result I had less to edit on a rock track I wrote that has lots of stops in it. I double-tracked one guitar with the 57 and the other [double tracked, same amp - same guitar - same settings] with the 609. I ended up gating the SM57, but there was no need with the 609.
Were I still a gigging musician I would get one of these for live use. The ability to hang it by the cord from the guitar amp and have the capsule pointed in the right direction is worth the ten dollars extra this mic is over a 57. That's one less mic stand to carry to a gig! I have seen people do that with a 57 but the tone was really lacking.
There are some mic companies that make great mics but in my opinion overcharge for them. One being Sennheiser [the MD421 is a wicked mic - $380 though? And made out of plastic? With the weakest and most ridiculous mic clip ever designed?] and Audio Technica [their high end mics are nice, but for the same money they are asking you could get something leaps and bounds better from Shure or AKG].
There are lots of instrument mics out there, and there are many "classics". The SM57 is a great mic. It is however not a "see all/do all/end all" microphone. There are times that a 57 is not the best choice - though it is an effective all-purpose microphone. Same as the e609, it just happens that the 57 is more popular having a few decades of seniority. If you don't already have a 57, maybe you should pick up a e609 - one of your friends is bound to have a 57 you can borrow anyway.