Thinking of buying the HK Pilot mega 2.5 for my quadcopter, but i have seen quite some 'software issue' videos on youtube about this board. So i thought maybe i should ask what everyone has to say about it.
The reason i cant buy the original apm is my tiny Budget.


link to the product: http://hobbyking.com/hobbyking/store/__37328__HKPilot_Mega_V2_5_Flight_Controller_USB_GYRO_ACC_MAG_BARO.html

It depends on your luck or whatever you call it. What do exactly mean by software issues?
Most software issues are solvable but hardware issues are the ones to be afraid off. There are issues of blown 3.3v regulators on many APM 2.5's original as well as cloned. So whats important is the replacement policy of the seller.

I must warn you that its not for beginners, if you have worked with multirotors with FC's such as multiwi or have an idea of how arduino works, then it should be fairly easy, otherwise be ready to read a lot. Trust me there are lot of ways you can damage the board yourself by improper handling/wrong connection etc, so its important to know everything you can about APM 2.5.

If you want a cheaper APM 2.5.2 (Rs 3200 approx), then read below. My replacement FC is on the way.
http://www.rcindia.org/servos-gyros-and-all-electronics/apm-2-5-firmware-update-issue/

Also a link to a APM2.5 mega thread with every details you can find.
http://www.rcgroups.com/forums/showthread.php?t=2053670

Overall, if you can follow instructions easily and have some experience with programming FC's then go for it. Slowly add gps/telemetry etc as you get familiar with rest of the stuff. If you do get stuck somewhere, you can always find help here.

I have worked with kk2 board on my quad. Nothing more than that. I am confident about upgrading the APM to 3.1.  There are so many videos on YouTube about apm

Kk 2 is very simple but yeah it helps. If you are confident, then there is no issue.Yes, lots of support available with videos/threads/tutorials so very less to worry about. Upgrading firmware is the easy stuff, configuring it is the hard stuff. But since 3.1, there is auto tune which solves the PID tuning issue to a certain extent.
Anyways you should go ahead 

What do you exactly mean by configuring? Ya auto tune is good, I heard.

Configuring means there is rtl/rth, geo-fence, many different modes to fly such as acro/drift/sports/simple/super simple etc. You also need to be careful about placement of FC, gps module, telemetry module because of interference.Similarly there are 2 or 3 ways to power the FC, some of them are not suggested. Auto tune is not 100% effective, it depends on your frame,AUW, how have you distributed the weight etc.

Thats why I said you have lot of things you need to know about APM in the link I posted earlier otherwise you will end up frustrated while setup. Good thing is there is no dearth of support for APM 2.5
But Self help is the best help!

What do you exactly mean by configuring? Ya auto tune is good, I heard.

This looks like a good deal to me.http://www.aliexpress.com/item/APM2-6-ArduPilot-Mega-2-6-External-Compass-APM-Flight-Controller-Board/1554954115.html

Did you have any problems with your board?

available locally
at quadkopters.com at almost the same price as hk

Sir I am living in the UK, for my studies.

Ok then goodluckbuy.com has one for 57$
And with lea 6h gps for 97$
Cheapest price for amp flight control board