Kosos are pretty awesome, but they can be finnicky to fit. well, actually, the one time i helped someone out with a Koso install, it wasn't nearly as easy as one is led to believe. forget what kind of bike it was on though.
the Trail-Tech Vapor is incredibly awesome for the price. i've got one on my SV650S->N conversion. it's a fairly simple install. not as many bells & whistles as the Koso, but pretty much all you need for a streetbike. also, their customer service department is awesome. they were a real help the first time i futzed around with fitting a Vapor (which was a relatively new product at the time) to my FZR 5 or 6 years ago and no less helpful when i was fitting a Vapor to my current bike a couple months ago. if you don't want to spend a lot of money, this is an incredible value. and i can't really stress enough how awesome the company is. they also have an eBay store which i think you can get bike specific kits for a small discount over retail.
there's also the Veypor, which used to be quite popular, but i haven't heard much about them lately. it's closer to the Koso in price, and has a lot features (like the Koso) that make it seem more geared towards a racing setup. i.e. you'll be paying for a lot of features that you won't be using if it's just for your street ride.
lastly, there's the Electrosport (they're European and might be going under a different name these days) gauges. they look really nice and are between the Trail-Tech and the Koso in price. unfortunately, something happened to their American distributor and i've heard that since everything's based in Europe, customer service is abysmal/non-existent. OTOH, i hear there's a Chinese knock off of these gauges that you can find on eBay. but i haven't heard any user reviews on those.