Haven't checked out the specs of those TVs but for a PC, it's always recommended to go for a dedicated monitor rather than using an HDTV as a makeshift or permanent monitor.
An IPS paneled monitor will give you realistic and vivid color reproduction, greater viewing angles and deeper blacks (this is highly dependent upon the type of IPS panel used in a monitor; the ones using an eIPS panel are average in this respect like my PA238Q). As for an HDTV, these factors will depend upon the kind of panel it is using.
As for sharpness, it depends on the resolution of the TVs you are talking about. If they are 720p max, text sharpness will suffer. You'll be way better off with a full HD resolution monitor for that purpose.
Besides, TVs are just not meant to be used for close-up viewing for elongated periods of time. You will either end up straining your eyes or getting a headache. There have been a few examples of members here using a TV as a monitor only to dump that idea later on.
Tagging here the ones that come to mind,
Lord Nemesis,
Infected !
Yep, EternoMind is right. I used a plasma for like a year and now I am on a Dell 30"
Really its all good for movies and games,. but the biggest issue is the text, it is never clear enough,
and I have tried it on Panasonic Plasma, LG Led, Sony LCD, (We use about 15 HDTV's in the hotel so I can play around)
The best I love the Panasonic over the others, all were 1080p, but there is simply no comparison to an dedicated monitor.
As for OP's questions:
1.What will be the main difference between a IPS and an HDTV color reproduction wise?
Really depends on the TV.
2. Will the be any sort of Lag.....while watching movies /playing games ???
Again depends on the TV as well as Monitor both will have some amount of input lag, plasma's are better than LCD for this, but then CRT's are best, if this is your concern you might need some Gaming monitors with log Input lag
3. will reading be a problem .........i mean will letters appear sharp as monitors in a HDTV?
They are not a problem, one can read no issues, but they are not clear, i mean you should go and have a look, some HDTV's are terrible at it some are better,
one will have to check with the TV in the picture. I took my PC to the Panasonic shop before I paid them a penny to check how the TV responded to nVidia drivers and the font etc.
4. will the refresh rates be an issue for a TV? like wise will resolution be a problem?
No. All GPU's now give HDMI and the TV can ofcourse process that, even your sound will be via HDMI,
so problem with res etc. just stick to 1080p......Maybe while gaiming you might want to go down to 720p, depending on your card.
Get a Monitor.