Surge protectors are critical imo. I personally like APC as they have very good electronics in them, good filters etc… As for UPS, something most people don’t know is that there are two types of UPS systems (well more actually but 2 for our purposes.) Inline and (offline? forget the exact name atm ;p ) The inline one basically has the system disconnected from the wall outlet in that the ac powers the battery and does not get passed through to the unit at all. This type powers the system off of the battery by regenerating the equivalent of an ac signal going out to the system, so there is no direct connection to the external ac source. It therefore has no latency between when a power surge hits the UPS and when it disconnects the system from the surge. The other (not inline) type feeds the ac through to the system using surge protection hardware and uses the battery to fill in in case of a brownout (undervoltage from the power company.)
Ok, so the first one sounds better right? Well there is a problem. The generated ac in the case of the first one is not true ac, it is a (roughly square wave) from the dc battery. This generated wave is like sandpaper to the electronics of the system. In fact, the second type is more expensive and is better for the life of your components. This is ofc separate from the discussion of the overall quality of the unit.
This last is true of low cost systems. When it comes to a UPS, you truly get what you pay for. I’ve seen “low cost” UPS’s (even from APC) that have actually caught fire, destroyed electronics plugged in to them when the battery failed, and worse. If the UPS is 650VA or less, you’re wasting your money. What you have is a very expensive surge protector and low-cost/low-quality line conditioner. The batteries in these units usually have a life span of 18 months to 2 years. When they fail they can be more of a danger to the devices plugged into them than an electrical storm. Most of these units, including those from APC, are poorly built with little protection.
Between 650VA and 1400VA, it is a crap shoot. Some are better than others. APC makes some good units in this range, as does Tripp Lite. There are others in there as well, do your research here. Good 1400VA systems can be had for around $200US. These will usually have replaceable battery(ies) and are usually better built. The battery packs for this range will have life spans in the 2.5 to 4 year range. Replacement battery packs can cost as little as $50US and as much as a new unit.
1500VA-3000VA things are better as these units are more costly and usually contain better AC failover, line-conditioners, active surge controllers, and line condition monitoring and in some of the better units predictive protection. Some may even be 3-phase. 3000VA units can be had for less than $1000US.
Above 3000VA the features are absolutely delicious. These units are for larger servers and such. 20kVA units can be had for less than $10,000US and can protect a whole house. I’ve installed units as large as 80kVA for clients.