The Galaxy 5
The Samsung Galaxy 5 (http://www.gsmarena.com/samsung_i5500b-3371.php), was one of first reasonably priced Android phones to be released in India. I got this phone to first time experience a full touch phone, tired of endlessly waiting for Nokia to release its N9. This phone came with Android 2.1 (éclair), with some variants getting updated to Froyo. Mine was never updated. Exactly 1 year after I brought this phone, I was quite unhappy with the phone, Android and Samsung and happy switched to Lumia 800 on the launch day (also see: http://tovganesh.blogspot.in/search?q=lumia). Since then I have rooted this phone, have installed numerous builds of CyanogenMod, and once unsuccessfully tried to sell it off. But now finally found a real use of this phone: use it as mobile hotspot.
A day after I got my Lumia 800, I rooted my Galaxy 5 to install whatever build was available of CyanogenMod. It was pretty immature and unstable at that time. But it got better and better. psyke83, the main developer has even ported CyanogenMod 10.1 (which is basically Jellybean 4.x) for this device. But for my purpose, I found the CyanogenMod 7 ROM more stable. One thing good with Android, is that I can literally install my own OS once the device has been boot unlocked.
The Galaxy 5, with CyanogenMod 7 - http://madteam.co/forum/development-8/(dev)-cyanogenmod-7-2-0-rc1-galaxy5-port/ (or 10.1 - http://madteam.co/forum/development-8/(dev)-cyanogenmod-10-1-galaxy5-port-(androidarmv6)/) from psyke83 et al. is a solid replacement for the stock ROM (which was éclair).
To know about installing the CyanogenMod builds visit the development thread of madteam (http://madteam.co/forum/development-8/)
Using Galaxy 5 as Portable "mi-fi"
I had recently got a 3G data card from Vodafone India for internet access while travelling. Although, after buying this card I realized that my current service provider (Airtel), is also giving me pan-India roaming for data. However, the Airtel connection is a 2G service in my circle so is pretty much not useful when I want to remotely work while travelling. However, the dongle has additional problems: I have to always keep it connected to my laptop; many a times it has signal problem, moving around with laptop makes it quite uncomfortable. After searching for portable 3G routers, I decided to experiment with using my Galaxy 5 as a mobile router instead. The Galaxy 5 is a 3G phone and the CynogenMod ROM provides with options of tethering the data connection. More over the Vodafone data card is a SIM based solution, essentially allowing me to use the SIM in any phone or device, without the data card.
I use the custom power widget to make switching on an off the 3G hotspot easier. I have also installed the MyDataManager app (https://play.google.com/store/apps/details?id=com.mobidia.android.mdm) to give me an idea of how much data is be consumed.
Battery life and Performance
Have used this setup only for 24 hours, and that too at home. So, I can truly comment on this only during my next travel. Having said that, the battery life seems to be pretty descent, lasted for about 12 hours on descent usage. The 3G speeds are also pretty good at the place where I live.