OrangeHRMS seems to be a great effort and looks like will surely show its full impact by end of this year, when it will be feature rich!!
Some of my ideas...
Payroll is important and many are already requesting, but my opinion is that stay focussed on HRMS, till its all done, before entering ino numbers game!!
Tracking Contracts and Employment Period [duration, designation, salary] is one of the most pressing need in any HRMS [This can be related to recruitment and performance management for promotions, etc and later with payroll]
Though full Salary module can be thought of later as that has to be designed in very flexible way as many components of salary are country specific!!
Employee Expenses is also another important feature, most will like to have
Don't make your application too much US specific [SSN, etc], as there's world outside US as well.
The forms [ideally all], should have an option to add or remove fields depending upon the requirement. Take ques from SugarCRM/vtigerCRM. This has to be taken into care from the beginning as later will be bit difficult to implement and believe me this feature alone will raise value of OH by tons.
In education, why you added Institute, this will increase a lot of combinations to be ceated by admin, my advice break it into separate forms and can add some more details like year of completion, grade, etc.
I'm not sure if all this is worth 2 cents or not, still its IMHO is what i think is needed.
Keep up your good work!!