Will and I7 4790 be compatible with a H81 motherboard?

Solution
http://ark.intel.com/products/80806/Intel-Core-i7-4790-Processor-8M-Cache-up-to-4_00-GHz
is the link to the processor which says that is is a LGA 1150 socket.

http://uk.pcpartpicker.com/part/asus-motherboard-h81iplus is the link you gave for the motherboard and http://www.asus.com/Motherboards/H81IPLUS/specifications/ is the official link for the manufacturer of the motherboard saying that the motherboard is a LGA 1150 socket.

http://www.asus.com/Motherboards/H81IPLUS/HelpDesk_CPU/ is the link of official supported CPUs and the i7-4790 is on it.

So, yes they will work together.
http://ark.intel.com/products/80806/Intel-Core-i7-4790-Processor-8M-Cache-up-to-4_00-GHz
is the link to the processor which says that is is a LGA 1150 socket.

http://uk.pcpartpicker.com/part/asus-motherboard-h81iplus is the link you gave for the motherboard and http://www.asus.com/Motherboards/H81IPLUS/specifications/ is the official link for the manufacturer of the motherboard saying that the motherboard is a LGA 1150 socket.

http://www.asus.com/Motherboards/H81IPLUS/HelpDesk_CPU/ is the link of official supported CPUs and the i7-4790 is on it.

So, yes they will work together.
 
Solution
Hey,
Minor points:

1) The BIOS update for support of the new CPU's was done in January 2014. That SHOULD mean that recent motherboards ship with that BIOS.

2) Is the i7-4790 the best CPU for you?

The i7-4790K works at 4.4GHz Turbo by default (i7-4790 is 4GHz) so it has 10% more processing power. It is apparently also easily overclocked higher.

Even if you get the SAME motherboard the i7-4790K should work at 4.4GHz just no higher.
 


Interesting, although I'm weary on the price point of the K version, do you by any chance know what it will be?
 

$350 on intel site
You can preorder it for $340
http://www.newegg.com/Product/Product.aspx?Item=N82E16819117369
So UK price i guess would be around £230-£250
 


Well i am going to build a mini itx system for CAD, Heavy workloads, As a personal computer and some gaming. Also I picked the i7 (please forgive for saying this) to be 'futureproof' for the upcoming years.
 

For your need I would save some money and buy an I5 4690 which should be enough. If you need extra performance then go ahead and buy the i7-4790 there won't that much of a performance different between that and the K version unless your overclocking.
If you really what to be "futureproof" I waiting for the ddr4 motherboard coming in 2015