Upgrading old mac
Hello all,
I agree the SSD upgrade is worth it. Personally, I let OWC upgrade me big time with 2x 480GB SSDs and yes, it is only SATAII since i have the iMac mid-2010 but this machine is fully beefed up so it is worth it to me. All the more that I plan to strip them in RAID 0 and reach (in theory) 560GB/s sustained throughput, something not even all mordern SSDs do. Thru some experience I know the soft RAID of Mac OS is very fast. I just hope I can indeed boot on such a drive, but I believe yes. With a 2.97GHz quad code i7 and 32GB RAM (yes it works, 4x 8GB), I think it is totally worth it. (wish it was retina though). I need to shell out at least twice as much for any new Mac that will perform half as fast. Of course the proof is in the pudding and so if you are interested I'll post back when I get my Mac back, with my impressions and some Black Magic numbers to chew on.
I cannot speak for doing it yourself as I chose to let a company do it.
However I have a comment on something that I read here: some posters disqualify using an SSD over FW800 as some other posters proposed to the OP. I would NOT disqualify this and certainly recommend it as a valid alternative if you want something that works today, for cheap, and based on my experience the performance can be very good. Here's the story: As I am transitioning how I manage my data I happen to have worked on my large Aperture library (35k images) with many large RAW files (25MB a pop) over USB2.0 with a top notch SSD (850PRO 1TB), while Mac OS and Aperture were on the stock 2TB HDD before my SSD upgrade. This was obviously a (temporary) ridiculous setup, but felt MUCH FASTER that working all on the stock HDD. Even over USB2.0 with is half as fast as FW800. Here's my theory: the bus throughput matters a lot if you transfer large amounts at once. In my setup, the speed came from ultra fast data access with limited size data transfers (images loaded one by one, and Aperture library is millions of very small files). In real life, this covers most applications but the heaviest ones. For this reason an SSD over FW800 will still be a night & day improvement over an old HDD to any old Mac user. It is cheap and can be done today without opening your mac or shipping it to someone. So it is a valid choice IMHO.
Give me heat if you disagree

but we all easily agree that a SSD has a place somewhere (inside and/or out) our old macs
Personally I'm doing both as my mac upgrade includes an eSATA port to use my top notch SSD with the fastest port that old mac has (and yes, with faster ports on another newer mac too, the whole point of my setup is to easily have my data with me across more than one mac).
Cheers,
Davy