This is my 2nd 1999-2004 WJ Grand Cherokee, and my 3rd Jeep, as I've had a 1997 XJ Cherokee as well.
I bought this Jeep solely to do camping, fishing, MTBing, and general holiday trips. It is not a daily driver, nor a Soccer Mum's car...
I bought this Jeep at a bargain price, as the previous owner did not know how, and did not want to spend the money on fixing the above issues. I've fixed them all, and made it reliable and nice to drive for a small cost.
For the money that I've put into this vehicle, you could not buy another make or model that has the same level of comfort, power, and economy.
Once you understand how the vehicle works (mechanical and electrics), you can easily diagnose and fix anything. The beauty of owning a Jeep is that all the info is on the Internet, so you can very easily find out what you need to know.
I also use a OBD2 (diagnostic port under the dash) reader to read the ECU and check for fault codes (like the P0108), which makes finding faults really easy. You can also get these readers for your smartphone (search OBD2 in your app store).
The power from the 4.7 V8 is excellent, along with the 545RFE transmission. It's not the most powerful V8, but the WJ is relatively light compared to most other SUV/4wd's in its class.
Economy wise, driving in the city I am getting 13.5-14.5L/100km, and in the country 10.5-12L/100km, depending on the amount of hills and how much I've filled it with camping gear.
I also have the 'Quadradrive' 4wd system (was optional from the factory, and stock on the 'Overland' models) which is great offroad. Essentially when a wheel is slipping/spinning offroad and you are losing traction, the diffs will transfer the torque to the other wheel on the axle, allowing you to gain traction. The system is about 90% as good as having aftermarket lockers in your diffs. There is no other vehicle in this price point on the 2nd hand market that'll have a 4wd system of this capability (do not be confused with 'brake traction control' systems that claim to do the same thing; they are nowhere near as effective as proper 'torque sensing' or 'locking' differentials).
My first WJ Grand Cherokee was a 2003, and I put a 4" lift kit and ran 32" (265/70R17) tyres on it and a rear auto diff locker (as I did not have the 'Quadradrive' system). I did approx 35,000kms in it just driving on camping trips and offroad, spending a lot of time on corrugated dirt roads etc. Never had a major problem with this Jeep, only the usual wear and tear items (i.e. brakes, 1 CV joint, general maintenance), but no failures or anything.
If you're looking to buy one, ensure that it has had a solid service history. Any modern vehicle (say from 2000 onwards) MUST have regular oil changes. Due to all the emission regulations coming out, manufacturers are forced to come up with ways to reduce make their vehicles greener, and what this usually ends up in is carbon build up inside the motor (especially on modern turbo diesel engines). Therefore it is very important to keep the oil clean by changing it religiously. Also installing a 'oil catch can' on one of the inlet vacuum lines will help to minimise the amount of oil in the inlet side of the motor (and therefore keep all the sensors and throttle body clean, and allow them to work properly).
I change my oil and filter every 5,000km.
Make sure the cooling system is in great shape; do not ever let any part of the cooling system go faulty! The 4.7 V8 has a cast iron block and alloy heads, and their reaction to heat is different. This is the same for all vehicles with iron blocks and alloy heads; if they are allowed to overheat, then they expand and contract at different rates, and the chance of blowing a head gasket or warping/cracking a head or other failures head is very high.
Generally I have found the cooling system (i.e. radiator, water pump, thermostat, hoses, overflow bottle, etc) to be very capable and efficient, but don't be fooled by its efficiency; keep on top of it!
The WJ Grand Cherokee is perfect for someone who wants to drive something different, with heaps of power, good economy relative to the amount of power it makes (obviously a 2.0L 4cyl soft roader is going to be more economical, but it's not in the same class..), massive levels of interior comfort, live axle 4wd (not many of these left), excellent offroad capability in stock form (especially if it has the Quadradrive system), and if you are willing to do some Google searching on any issues faults that may arise in order to save money and understand the issue, before handing it over blindly to a mechanic, this vehicle will probably suit you.